Spacewar!
was conceived in 1961 by Martin Graetz, Stephen Russell, and
Wayne Wiitanen. It was first realized on the PDP-1 in 1962 by
Stephen Russell, Peter Samson, Dan Edwards, and Martin Graetz,
together with Alan Kotok, Steve Piner, and Robert A Saunders.
Spacewar! is in the public domain.

You
can play the original version on this website here!
Martin Graetz provided a printed version of the source. After
it was typed in in again - it was about 40 pages long - it was
re-assembled with a PDP-1 assembler written in PERL. The resulting
binary runs on a PDP-1 emulator written as a Java applet. The
code is extremely faithful to the original. There are only two
changes. 1)The spaceships have been made bigger and 2) The overall
timing has been special cased to deal with varying machine speeds.

The
"a", "s", "d", "f" keys control one of the spaceships. The "k",
"l", ";", "'" keys control the other. The controls are spin
one way, spin the other, thrust, and fire.